The present invention relates to a device to be fitted on a vehicle wheel of a predetermined size in order to increase the friction between the wheel and the road surface during winter conditions, comprising a belt made substantially from textile material and intended to encircle the tread of the wheel and be held in place by means of flexible inner and outer side portions which, at least on the inner side of the wheel, is tightened by means of an elastic member.
Such a device is known from U.S. Pat. No. 2,682,907, FIGS. 1-3. This known device is symmetrical about its middle plane and is made from a single piece of coarse canvas, which is folded over so that along either of the two outer edges a continuous pocket is formed which receives an elastic member in the form of a helical spring.
The middle portion of the device, which is supposed to constitute the belt to come into contact with the road surface, is by means of glue provided with a coating of aluminium oxide impregnated with abrasive particles in order to substantially increase the friction against the road surface.
The device according to U.S. Pat. No. 2,682,907 is formed to cling quite closely to the vehicle wheel and cannot be put in place on the wheel when the wheel is mounted on a vehicle unless the wheel is raised from the ground. Since the device is symmetrical with flexible side portions having springs included on both sides, the device, e.g. when driving through a curve on a dry road surface, conceivably could creep off the wheel towards the inside thereof and impede the steering mechanism of the vehicle, possibly also damage brake lines. Once the device has moved to the inner side of the wheel, it cannot be removed without destroying the device or removing the wheel from the vehicle.